Magnum was a class ofSIGINTspy satellites reportedly operated by theNational Reconnaissance Office (NRO) for theUnited StatesCentral Intelligence Agency (CIA). The program remainsclassified, and the information that exists is speculative.

It is believed that two Magnum satellites were launched fromSpace Shuttle Discovery (OV-103) during the missionsSTS-51-C in 1985 andSTS-33 in 1989. The satellites reportedly have a mass of 2,200–2,700 kg (4,900–6,000 lb), operating in near-geosynchronous orbits, usingInertial Upper Stages (IUS) to get from the shuttle's orbit to the higher geosynchronous orbit.^[1] According toJim Slade ofABC News, the second satellite,USA-48, replaced the first,USA-8, which after more than four years in orbit was running out of maneuvering fuel required for keeping its station over theIndian Ocean. The mission of the two satellites was to listen in to military and diplomatic communications from theSoviet Union,China, and neighboring countries.^[2]

USA-67, launched aboardSpace Shuttle Atlantis (OV-104) in November 1990 (STS-38 mission), was initially identified as a third Magnum satellite owing to the presence of two upper stages in orbit after its deployment, suggesting that an Inertial Upper Stage (IUS) had been used to deploy it. It was later determined that the second upper stage was from the stealthyProwler spacecraft, and that USA-67 was aSatellite Data System (SDS-2)communications satellite.^[3][4]

The Magnum satellites, built byTRW, are rumored to have large (estimated 100 m (330 ft) diameter)^[5][6] umbrella-likereflecting dishes to collectRFsignals fromEarth. The Magnum/Orion satellites replaced the olderRhyolite/Aquacade series of SIGINT satellites, and have themselves been succeeded by theMentor/Advanced Orion satellites.

• Orion

• Richelson, Jeffrey T.; ed.U.S. Military Uses of Space, 1945-1991, Vol. 1, Guide, National Security Archive, 1991

• Information from astronautix.com
• Gunter's Space Page - information onMagnum
• Globalsecurity-Magnum/ Mentor/ Orion

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